绘制多边形时出现ArrayIndexOutOfBoundsException错误 [英] ArrayIndexOutOfBoundsException error while drawing a polygon

问题描述

我在尝试绘制多边形时遇到了麻烦.首先，当我尝试使用addPoint(int x, int y)方法绘制多边形并逐个给出坐标时，没有问题，多边形可以完美绘制.但是，如果我将坐标作为数组(x坐标和y坐标的整数数组)给出，则编译器会出错.如您所见，这是工作代码，

hi there i'm having a trouble while i'm trying to draw a polygon. first of all, when i try to draw a polygon with using addPoint(int x, int y) method and giving coordinates one by one there is no problem, polygon could be drawed perfectly. however, if i give the coordinates as an array (an integer array for x coordinates and y coordinates) compiler gives error. this is the working code as you can see,

@Override
public void paint(Graphics g) {

    Graphics2D g2 = (Graphics2D) g;

    Polygon poly = new Polygon();

    poly.addPoint(150, 150);
    poly.addPoint(250, 100);
    poly.addPoint(325, 125);
    poly.addPoint(375, 225);
    poly.addPoint(450, 250);
    poly.addPoint(275, 375);
    poly.addPoint(100, 300);

    g2.drawPolygon(poly);

}

但是如果我使用xpoints和ypoints数组(在Graphics类中为多边形定义)，它将无法正常工作.

but if i use the xpoints and ypoints array (which are defined in Graphics class for polygon) it doesnt work properly.

@Override
public void paint(Graphics g) {

    Graphics2D g2 = (Graphics2D) g;

    Polygon poly = new Polygon();

    poly.xpoints[0]=150;
    poly.xpoints[1]=250;
    poly.xpoints[2]=325;
    poly.xpoints[3]=375;
    poly.xpoints[4]=450;
    poly.xpoints[5]=275;
    poly.xpoints[6]=100;      

    poly.ypoints[0]=150;
    poly.ypoints[1]=100;
    poly.ypoints[2]=125;
    poly.ypoints[3]=225;
    poly.ypoints[4]=250;
    poly.ypoints[5]=375;
    poly.ypoints[6]=300;

    g2.drawPolygon(poly.xpoints, poly.ypoints, 7);

}

如果您能为您提供帮助和感谢，我将不胜感激.

i will appreciate if you can help and thanks anyway.

推荐答案

来自您的评论:

我认为应该是7，因为有7个整数元素 每个数组?

i thought that it should be 7 cause there are 7 integer elements for each array ?

您必须先initialize your array然后是populate the array with elements.

    poly.xpoints = new int[7]; // initializing the array
    poly.xpoints[0]=150;       //populating the array with elements.
    poly.xpoints[1]=250;
    poly.xpoints[2]=325;
    poly.xpoints[3]=375;
    poly.xpoints[4]=450;
    poly.xpoints[5]=275;
    poly.xpoints[6]=100;  

YPoints同样适用.

Same applies to YPoints as well.

如果您正在寻找动态阵列，请使用 列表 从Java集合框架(如ArrayList)实现类.

If you looking for a Dynamic Array use one of the List implementing class's from Java collection Framework like ArrayList.

List<Integer> xPoints = new ArrayList<Integer>();
xPoints.add(150);
xPoints.add(250);
...

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